AC surface PDs in air from a triple junction (TJ) of cylindrical insulator with a backing electrode were decreased by a use of the hollow type electrode. The voltage applied was changed in a range from 1 to 1.5 times of an initiation of PD (Vpd). The thickness of the insulator was changed in a range from 2mm to 7.5mm. In the cases of 1.2x(Vpd) of the applied voltage and 7.5mm of the thickness, the integrated magnitude of the PD pulses for the electrode with hollow was about 80% smaller than that for the electrode without hollow; the integrated number of the pulse event was 40-50% smaller than that for the one without hollow; the PD pulses of which magnitude was stronger than approximately 7×10^-1 C were suppressed significantly. The computing calculation of an electric field around the TJ suggested that the generation and propagation of the PD pulse resulted from the increase in potential and strength of the vertical field component on the surface of an insulator near the TJ. It was observed from dust figures that the propagation of PDs on the insulator with the hollow was controlled their length about 50% shorter than that on the insulator without the hollow.